Implanted multichamber cardiac device with selective use of reliable atrial information

Abstract

An implantable medical device acquires a first cardiac signal in a first heart chamber and a second cardiac signal in a second heart chamber. The device determines if the first signal is unreliable. In response to determining the first signal to be unreliable, the device switches from a first cardiac arrhythmia detection mode of operation to a second cardiac arrhythmia detection mode of operation, the first detection mode requiring the use of both the first cardiac signal and the second cardiac signal and the second detection mode requiring the use of the second cardiac signal and not requiring the use of the first cardiac signal.

The invention claimed is: 
     
       1. A method for use in an implantable medical device for detecting cardiac arrhythmias in a patient, the method comprising:
 acquiring a first cardiac signal in a first heart chamber, the first cardiac signal comprising events corresponding to activations of the first heart chamber; 
 acquiring a second cardiac signal in a second heart chamber, the second cardiac signal comprising events corresponding to activations of the second heart chamber; 
 determining whether the first signal is unreliable; and 
 switching from a first cardiac arrhythmia detection mode of operation to a second cardiac arrhythmia detection mode of operation in response to determining the first signal to be unreliable, the first detection mode corresponding to using both the first cardiac signal and the second cardiac signal, and the second detection mode corresponding to using the second cardiac signal and not the first cardiac signal. 
 
     
     
       2. The method of  claim 1 , wherein determining whether the first cardiac signal is unreliable comprises:
 determining a morphology of the first signal; and 
 detecting signal artifact in response to the determined morphology. 
 
     
     
       3. The method of  claim 1 , wherein determining whether the first cardiac signal is unreliable comprises:
 determining an amplitude of the first cardiac signal; 
 comparing the determined amplitude to a sensing threshold; and 
 determining whether the first cardiac signal corresponds to a low amplitude signal in response to the comparing. 
 
     
     
       4. The method of  claim 1 , wherein determining whether the first cardiac signal is unreliable comprises:
 determining a time interval between activations of the first heart chamber; 
 comparing the determined time interval to a long pause threshold; and 
 determining undersensing of the activations in response to the comparing. 
 
     
     
       5. The method of  claim 1 , wherein determining whether the first cardiac signal is unreliable comprises determining whether activations sensed from the first cardiac signal occur simultaneously with activations sensed from the second cardiac signal. 
     
     
       6. The method of  claim 1 , wherein the first cardiac arrhythmia detection mode comprises determining a relation between activations sensed from the first cardiac signal and activations sensed from the second cardiac signal, and wherein switching from the first mode to the second mode comprises disabling determining the relation between activations sensed from the first cardiac signal and activations sensed from the second cardiac signal. 
     
     
       7. The method of  claim 1 , wherein the first cardiac event detection mode comprises:
 determining a first rate of activations sensed from the first cardiac signal; 
 comparing the first rate to a second rate of activations sensed from the second cardiac signal; and 
 enabling a morphology analysis of the second cardiac signal in response to the comparing, wherein switching from the first mode to the second mode comprises: 
 disabling determining the first rate of activations sensed from the first cardiac signal and the comparing; and 
 enabling the morphology analysis of the second cardiac signal. 
 
     
     
       8. The method of  claim 1 , further comprising:
 monitoring the first cardiac signal, in response to determining the first cardiac signal is unreliable, to determine whether the first cardiac signal is no longer unreliable; and 
 switching from the second cardiac arrhythmia detection mode to the first cardiac arrhythmia detection mode in response to determining the first cardiac signal is no longer unreliable. 
 
     
     
       9. The method of  claim 1 , further comprising disabling therapy delivery in the first cardiac chamber in response to switching to the second arrhythmia detection mode of operation. 
     
     
       10. The method of  claim 1 , wherein the first cardiac signal is an atrial electrical signal and the second cardiac signal is a ventricular electrical signal. 
     
     
       11. The method of  claim 1 , wherein determining whether the first signal is unreliable comprises analyzing the first signal to determine an indicator of whether the first signal is unreliable for use in cardiac arrhythmia detection. 
     
     
       12. An implantable medical device for detecting cardiac arrhythmias in a patient, comprising:
 a first sensor to acquire a first cardiac signal in a first heart chamber, the first cardiac signal comprising events corresponding to activations of the first heart chamber; 
 a second sensor to acquire a second cardiac signal in a second heart chamber, the second cardiac signal comprising events corresponding to activations of the second heart chamber; 
 a processor configured to receive the first and second cardiac signals and to determine whether the first cardiac signal is unreliable, switch from a first cardiac arrhythmia detection mode of operation to a second cardiac arrhythmia detection mode of operation in response to determining the first signal to be unreliable, the first detection mode corresponding to using both the first cardiac signal and the second cardiac signal, and the second detection mode corresponding to using the second cardiac signal and not the first cardiac signal. 
 
     
     
       13. The device of  claim 12 , wherein determining whether the first cardiac signal is unreliable comprises:
 determining a morphology of the first signal; and 
 detecting signal artifact in response to the determined morphology. 
 
     
     
       14. The device of  claim 12 , wherein determining whether the first cardiac signal is unreliable comprises:
 determining an amplitude of the first cardiac signal; 
 comparing the determined amplitude to a sensing threshold; and 
 determining whether the first cardiac signal corresponds to a low amplitude signal in response to the comparing. 
 
     
     
       15. The device of  claim 12 , wherein determining whether the first cardiac signal is unreliable comprises:
 determining a time interval between activations of the first heart chamber; 
 comparing the determined time interval to a long pause threshold; and 
 determining undersensing of the activations in response to the comparing. 
 
     
     
       16. The device of  claim 12 , wherein determining whether the first cardiac signal is unreliable comprises determining whether activations sensed from the first cardiac signal occur simultaneously with activations sensed from the second cardiac signal. 
     
     
       17. The device of  claim 12 , wherein the first cardiac arrhythmia detection mode comprises determining a relation between activations sensed from the first cardiac signal and activations sensed from the second cardiac signal and wherein switching from the first mode to the second mode comprises disabling determining the relation between activations sensed from the first cardiac signal and activations sensed from the second cardiac signal. 
     
     
       18. The device of  claim 12 , wherein the first cardiac event detection mode comprises:
 determining a first rate of activations sensed from the first cardiac signal; 
 comparing the first rate to a second rate of activations sensed from the second cardiac signal; and 
 enabling a morphology analysis of the second cardiac signal in response to the comparing, and wherein switching from the first mode to the second mode comprises: 
 disabling determining the first rate of activations sensed from the first cardiac signals and the comparing; and 
 enabling the morphology analysis of second cardiac signal. 
 
     
     
       19. The device of  claim 12 , wherein the processor is further configured to monitor the first cardiac signal, in response to determining the first cardiac signal is unreliable, to determine whether the first cardiac signal is no longer unreliable, and switch from the second cardiac arrhythmia detection mode to the first cardiac arrhythmia detection mode in response to determining the first cardiac signal is no longer unreliable. 
     
     
       20. The device of  claim 12 , further comprising a therapy delivery circuit to deliver a therapy in response to detecting a cardiac arrhythmia, wherein the processor is configured to disable therapy delivery in the first cardiac chamber in response to switching to the second arrhythmia detection mode of operation. 
     
     
       21. A non-transitory computer-readable medium storing a set of instructions in an implantable medical device for performing a method comprising:
 acquiring a first cardiac signal in a first heart chamber, the first cardiac signal comprising events corresponding to activations of the first heart chamber; 
 acquiring a second cardiac signal in a second heart chamber, the second cardiac signal comprising events corresponding to activations of the second heart chamber; 
 determining whether the first signal is unreliable; and 
 switching from a first cardiac arrhythmia detection mode of operation to a second cardiac arrhythmia detection mode of operation in response to determining the first signal to be unreliable, the first detection mode corresponding to using both the first cardiac signal and the second cardiac signal, and the second detection mode corresponding to using the second cardiac signal and not the first cardiac signal.